Repeating a string with recursion, beginner

Question

I'm supposed to write a simple method that returns given string for given amount, seperated by comma (and no comma in the end), with recursion. If there are less than two counts, the return is empty string "".

final static String COMMA = ", ";
public static String replicate(String s, int count) {
    String answer = "";
    if (count < 2) {
        return answer;
    }
    else {
        answer = s + COMMA + replicate(s, (count - 1));
        return answer;
    }
}

If I put s = cat and count = 5, I get cat, cat, cat, cat,- One short what I need. I'm at my wits end here what to do, to get proper amount of repeats here without the comma at the end.

EDIT: Clearly I failed to communicate, that the method SHOULD return an empty string, if the count is two or less. Sorry for the lack of clarity there.

Try String answer = s;...

Usagi Miyamoto
– Usagi Miyamoto

2019-12-09 16:16:46 +00:00
Commented Dec 9, 2019 at 16:16 — Usagi Miyamoto
– Usagi Miyamoto, Commented Dec 9, 2019 at 16:16

Nick Reed · Accepted Answer · 2019-12-09 17:45:36Z

1

You're extremely close! When you hit your base case count < 2, instead of returning an empty string, you can return your input string. Be sure to check that length isn't 0, too.

EDIT: from information in the comments, you want to return an empty string for any counts less than or equal to two. Odd requirement, but this will fit that issue; it uses three as a base case instead of two, returning three s inputs concatenated together.

  final static String COMMA = ", ";
  public static String replicate(String s, int count) {
      String answer = "";
      if(count <= 2) {
        return answer;
      }
      if(count == 3) {
        return (s + COMMA + s + COMMA + s);
      }
      else {
          answer = s + COMMA + replicate(s, (count - 1));
          return answer;
      }
  }

Demo

edited Dec 9, 2019 at 17:45

answered Dec 9, 2019 at 16:17

Nick Reed

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6 Comments

JustAnotherDoomer Over a year ago

Thank you for your answer! I failed to say that the method should return the empty string in case of two or less count - this answer returns still the given string with count one.

Nick Reed Over a year ago

Something must've been lost in translation then. What should the return values be for replicate("cat", 2) and replicate("cat", 1)?

JustAnotherDoomer Over a year ago

For String repeat = replicate("cat", 1) = ""; and String repeat = replicate("cat", 2); repeat = "cat, cat";

Nick Reed Over a year ago

Weird requirement, but okay! Answer and demo updated.

JustAnotherDoomer Over a year ago

Thank you very much! I was thrown off by that requirement also, but playing around the base seemed to work evidently.

|

Joop Eggen · Accepted Answer · 2019-12-09 16:18:16Z

0

Every element is there, just a bit unreadable code.

If count is 0, "".
If one, s itself.
Otherwise s, + recursive result.

So:

public static String replicate(String s, int count) {
    if (count <= 0) {
        return "";
    } else if (count == 1) {
        return s;
    } else {
        return s + COMMA + replicate(s, count - 1);
    }
}

What lead to mental failure was the variable answer, and the two cases of < 2.

answered Dec 9, 2019 at 16:18

Joop Eggen

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Comments

Amjad Nassar · Accepted Answer · 2019-12-09 16:28:53Z

0

public static String replicate(String s, int count) {

    if (count >= 2) {
        s = s + COMMA + replicate(s, --count);
    }
    return s;
}

replicate("hii", 4) --> return "hii,hii, hii, hii"

COMMA + replicate("hii", 3) --> return "hii, hii, hii" COMMA + replicate("hii", 2) --> return "hii, hii" COMMA + replicate("hii", 1) --> return "hii"

answered Dec 9, 2019 at 16:28

Amjad Nassar

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